1. Field of the Invention
The present invention generally relates to methods of measuring ion-concentration and the like and a calibrating sheet as well as a calibrating method of measuring devices used therein.
2. Description of the Prior Art
In the case where various ion-concentrations, such as quantities of dissolved oxygen, conductivities and the like (hereinafter, ion-concentrations and the like) are in infinitesimal quantities of a liquid secreted from a living body and are measured, different sampling jigs have been used for every item to be measured to obtain a sample for the measurement.
For example, to sample saliva, a cotton roll has been put in an oral cavity to impregnate the cotton roll with the saliva. Then, the cotton roll has been subjected to centrifugal separation by means of a centrifugal separator to obtain saliva without impurities. To sample saliva from glandula parotis, a cup has been put on a mucous membrane of an oral cavity in an adhered manner to obtain an appointed saliva (prior art 1).
To sample sweat emanating from a surface of a body, a quantitative test method (QPIT method) has been used. For example, sweat from an arm has been absorbed by a filter paper and diluted to measure an ion-concentration. Or, an ion electrode and a conductivity electrode have been directly pressed against a skin perspiring sweat (prior art 2).
In addition, as to an ion-concentration, in particular, pH of a skin, an electrode whose glass electrode surface alone is a flat surface has been pressed against a skin (prior art 3).
Furthermore, a deterioration test of iron and steel subjected to a pretreatment for painting, painting of cars, painting of buildings, plated articles and the like may be carried out. For example, in the measurement of pH, pNa, pCl, conductivity and the like of contaminating substances adhered to a painted film on iron and steel, contaminating substances have been sampled by mopping up the painted film of an appointed area in an appointed direction and number of times by means of a gauze. The gauze was boiled in distilled water and impregnated with it; and by the use of a clean glove, the gauze is boiled in distilled water for one hour, and a total volume of 500 ml is made to obtain an appointed sample (prior art 4).
However, the prior arts have the following disadvantages, respectively.
That is to say, according to the prior arts 1, 2 and 4, to obtain a sample to be measured, considerable instruments are required and pretreatment is necessary. In short, a disadvantage is that great time and labor are required in the measurement. In the case of prior art 3, the measurement can be achieved only for a portion of skin capable of direct touching, and a quantity of KC1 leaked is increased, whereby the measured result cannot be distinguished from an influence by a solution.
In addition, merely a small amount of sample to be measured can be sampled, whereby it is difficult to achieve an accurate measurement of the items to be measured.
In the event that an electrode of a pH meter is calibrated, five kinds of standard buffer solution have been used, for which their preparation methods are provided by JIS. That is to say, the standard solution having pH of 1.68, 4.01, 6.86, 9.18 and 10.02, respectively, at 25.degree. C. has been used as a calibrating solution. The five kinds of standard buffer solution include an oxalate standard solution [0.05M-aqueous solution of potassium tetra oxalate KH.sub.3 (C.sub.2 O.sub.4).sub.2.2H.sub.2 O], a phthalate standard solution [0.05M-aqueous solution of potassium hydrogen phthalate C.sub.6 H.sub.4 (COOK) (COOH)], a neutral phosphate standard solution [0.025 M-aqueous solution of mono potassium phosphate KH.sub.2 PO.sub.4 +0.025M-aqueous solution of disodium phosphate Na.sub.2 HPO.sub.4 ], a borate standard solution [0.01M-aqueous solution of sodium borate (borax) Na.sub.2 B.sub.4 O.sub.7 0.10H.sub.2 O], and a carbonate standard solution [0.025M-aqueous solution of sodium hydrogen carbonate NaHCO.sub.3 +0.025M-aqueous solution of sodium carbonate Na.sub.2 CO.sub.3 ].
Pure water having a conductivity of 2.times.10.sup.-6 .OMEGA..sup.-1 cm.sup.-1 (at 25.degree. C.) or less has also been used in the preparation of the standard buffer solutions. For example, the oxalate standard solution is prepared by dissolving 12.71 g of potassium tetra oxalate (JIS K8474, for use in the measurement of pH) in the pure water so as to be 1 liter in total.
FIG. 15 shows a procedure of the conventional calibrating method. Referring to FIG. 15, "preservation" means that the prepared standard solution is preserved in a bottle made of high quality glass or polyethylene in a sealed manner. A calibrating solution including the standard solutions, which are prepared and preserved in the above described manner, in the form of a set is commercially sold as an accessory of a pH meter.
Since a pH meter can achieve a measurement with accuracy when calibrated, in the measurement of pH it is necessary to carry out a calibration if the need arises. Accordingly, the above described calibrating solution is indispensable. Setting aside measurements in the laboratory, where a measurement is conducted out of doors and on fields, it is necessary to carry the above described set of calibrating solutions and washings together with the pH meter. Attendant disadvantages are that the apparatus is remarkably bulky, the calibrating operation is remarkably difficult to conduct out of doors, and the calibration is difficult to accurately carry out. In short, the measurement of pH has been difficult to accurately carry out.